"The Haunting of Hill House" is quickly becoming a fan favorite, with everyone from film and TV critics to famous horror author Stephen King praising the new horror series. In interviews with various entertainment outlets, the show's director, writer, and producer Mike Flanagan, as well as the cast, has revealed many secrets about the show's journey from page to screen.

Here's what you should know.

This post contains spoilers for "The Haunting of Hill House."

1/

The story has been adapted for film before.

"Rose Red" aired in 2002.
ABC

Back in 1963, screenwriter Nelson Gidding adapted Jackson's novel into the screenplay for the film "The Haunting," with Julie Harris and Claire Bloom, directed by Robert Wise.

In the early '90s, Stephen King pitched a remake of "The Haunting of Hill House" to Steven Spielberg, under the name "Rose Red."

A complete script was written, but Spielberg wanted more action scenes, while King argued for more horror. After they mutually agreed to put the project on hold, King bought back the rights to the script, revised the story, and pitched it to producer Mark Carliner. It eventually aired as a miniseries called "Rose Red" in 2002.

Then, in 1999, the story was adapted again, into another film of the same name. Renowned horror director Wes Craven started to work on the project but eventually left. The final version of the film starred Liam Neeson and Catherine Zeta-Jones and was directed by Jan de Bont.

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This isn't director Mike Flanagan's first experience with horror.

He directed "Ouija: Origin of Evil."
Universal Pictures

Mike Flanagan, who created, wrote, and directed "The Haunting of Hill House" for Netflix, has made a name for himself with hit horror films including "Oculus," "Hush," "Before I Wake," "Ouija: Origin of Evil," and "Gerald's Game." He's also slated to direct the upcoming "The Shining" sequel, "Doctor Sleep."

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The cast was disturbed while shooting because the show was "grounded in reality."

Oliver Jackson-Cohen was spooked while filming.
Netflix

In an interview with Spot, actor Oliver Jackson-Cohen, who plays the adult Luke, said that the show is "grounded in reality."

"We are talking about ghosts and floating tall people and people with bent necks and all of these ghosts, but actually you swap that out for anything else traumatic as a child, and it kind of holds up," Jackson-Cohen said. "What's more terrifying is the state that this family is in and the dynamics and how these events have completely shattered and completely changed the course of every single sibling's life."

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There was initially more backstory about the house's previous residents.

Some extra scenes about the house were never shot.
Netflix

Flanagan planned to reveal much more about the previous residents-turned-ghosts who haunt Hill House, but the scenes were eventually cut from the final script.

"We had actually written and planned to shoot a complete history of Hill House," he said in an interview with Entertainment Weekly. "Every other episode would open with about a five-minute history thing narrated by Steven, from his book and we did take from Jackson that the first victim of the house died before anyone had ever really stepped foot in it."

"We had built a really complex history of the Hill family that we ultimately didn't shoot," Flanagan explained. "We didn't have the time or the money to shoot it, which really broke my heart at the time, but we figured if we had to focus on anything, we had to focus on the Crain family."

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There are hidden figures in the background of many shots throughout the series.

You'll see ghosts throughout if you look carefully.
Netflix

If you thought you saw a ghost hiding in plain sight at any point in the show, you were likely correct. In an interview with Vulture, Flanagan said, "We actually hid dozens of ghosts throughout the series, in plain sight, in the deep background of shots. We don't call any attention to them, but they're there. If you look in a door frame, or under the piano, or behind a curtain in a lot of otherwise ordinary scenes, you'll see someone there."

The show originally had a different, darker ending.

A different ending had the family never leaving the house.
Netflix

The final episode of "The Haunting of Hill House" is different from the previous ones, in that it doesn't ultimately aim to scare. The season ends on a bittersweet note, with the characters coming out of the experience with a renewed sense of hope. Flanagan told The Hollywood Reporter that he initially had a very different ending in mind. He said his original idea for the ending would have implied that the family never leaves, but that he changed it because it felt too "cruel."

"We toyed with the idea for a little while that over that monologue, over the image of the family together, we would put the Red Room window in the background," Flanagan said. "For a while, that was the plan. Maybe they never really got out of that room. The night before it came time to shoot it, I sat up in bed, and I felt guilty about it. I felt like it was cruel. That surprised me. I'd come to love the characters so much that I wanted them to be happy. I came into work and said, 'I don't want to put the window up. I think it's mean and unfair.' Once that gear had kicked in, I wanted to lean as far in that direction as possible. We've been on this journey for 10 hours; a few minutes of hope was important to me."

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It's based on a 1953 novel of the same name.

The book and show, however, have some obvious differences.
via Netflix

"The Haunting of Hill House" is considered to be a reimagining of the book by Shirley Jackson, who is known for her work in the horror and mystery genres. Stephen King called "The Haunting of Hill House," Jackson's fifth novel, one of the most important horror novels of the twentieth century, according to The Guardian.

Nerdist pointed out that there are a number of phrases that are taken directly from Jackson's book and repeated throughout the series. They include: "cup of stars," "journeys end in lovers meeting," "in the night, in the dark," and the line, "I am home, I am home; now to climb." Additionally, the famous opening paragraph of the novel also bookends the show, with Steven Crain reading a version of it from his nonfiction account of his family's stay at Hill House. There are some variations from the original text, however.

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If there were to be a second season, it wouldn't focus on the Crains.

He's considering exploring more about the house.
Netflix

A second season of the wildly popular show isn't yet in the works, but it's likely only a matter of time. If Netflix were to order a new round of episodes, however, Flanagan said the story wouldn't revolve around the characters from season one.

He told Entertainment Weekly that while there isn't a concrete plan for a season two, he could potentially see the show moving forward as an anthology, with each season telling a different story with new characters. He explained that "the show is about haunted places and haunted people ... and there's no shortage of either … There's any number of things we could do, in or out of Hill House."

"I don't want to speculate too much about season two until Netflix and Paramount and Amblin let us know if they want one," Flanagan said. "What I will say, though, is that as far as I've ever been concerned with this, the story of the Crain family is told. It's done. I think that there are all sorts of different directions we could go in, with the house or with something completely different. I love the idea of an anthology as well."

He added, "I felt like the Crains have been through enough, and we left them exactly as we all wanted to remember them, those of us who worked on it. We toyed with a cliffhanger ending and we toyed with other ideas, but ultimately, in the writers' room and with the cast and everything else, we really felt like the story demanded a certain kind of closure from us and we were happy to close the book on that family."

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It was shot like a "10-hour movie."

It was a lot of hard work for the cast.
Photo by Steve Dietl / Netflix

Rather than shooting the film episode by episode, Mike Flanagan told Collider it was shot like a movie making it "exhausting" to shoot.

"We shot it like we were doing a 10-hour movie. We cross-boarded it like a movie. We would do blocks of three episodes at a time, all cross-boarded around each other. So, it felt like we were making five movies, back to back. It was exhausting," Flanagan said.